One of the important properties that high molecular weight materials for medical use such as artificial blood vessels, indwelling blood vessel catheters, and artificial dialysis membranes, are required to possess is an antithrombic property which prevents such foreign objects from inducing thrombosis on contact with blood. Generally, blood undergoes coagulation on exposure to an external foreign objects.
In the past, high molecular weight materials for medical use have been made antithrombic by various methods. Among the methods which confer an antithrombic property to high molecular weight materials there is the method comprising binding an anticoagulant to the high molecular weight material. Such method employs, for example, an ionic bond between heparin, a natural anticoagulant, and the cationic group present in the high molecular weight material (Japanese Patent Publication No. 42603/81 and Japanese Patent Application (OPI) No. 194/76. (the term "OPI" as used herein refers to a "published unexamined Japanese Patent Application"). Another method employs a covalent bond with heparin through introduction of an epoxy group into the high molecular weight material (Japanese Patent Application (OPI) No. 162701/82). In these methods, the bonding between heparin and the molecules of high molecular weight material is accomplished by first molding a high molecular weight material possessing a group capable of bonding with heparin in a desired form such as tube or film and subsequently impregnating the molded article with an aqueous heparin solution. Thus they entail complicated procedures and the obtained heparin-bound layers are only on the surface of the high molecular weight materials produced. Thus, the antithrombic property is not imparted to the interior sections of the tube or film. This drawback hinders the actual use of the products in suturation, fusion, and severance. Since the heparin is bound to the high molecular weight material only on the surface thereof, once the heparin on the surface is dissolved out, the high molecular weight material no longer possesses the antithrombic property. Thus, the products obtained by the conventional method have a disadvantage in that they only endure actual use for a relatively short period.